Leadless pacemaker bradycardia pacing functionality was assessed. The mean pacing threshold, R-wave amplitude and impedance at implant were 0.53 ± 0.42 V at 0.5 ms, 19.9 ± 9.9 mV and 727 ±193 Ω, respectively. S-ICD heart rhythm discrimination was correct during intrinsic and leadless pacemaker pacing above intrinsic rate and did not result in over-sensing. Unidirectional device-device communication from the S-ICD to the leadless pacemaker via conductive communication was successful in 306 out of 309 communication attempts in dorsal position of the animals. All anti-tachycardia pacing requests that were triggered by the S-ICD and received by the leadless pacemaker resulted in anti-tachycardia pacing therapy delivery. There was a small increase in pacing threshold (p < 0.001) and decrease in R-wave amplitude (p = 0.001) and impedance (p = 0.04) between baseline and 90 days of follow-up. The chronic device-device communication success was 100 percent and all communication signals were successfully translated into anti-tachycardia pacing delivery by the leadless pacemaker.

The first-in-man trials with validated and verified modular cardiac rhythm management (CRM) system are planned and will combine leadless pacemaker and ICD therapy in a coordinated fashion. According to the authors, the safety and performance results of the modular system are required to consider clinical adoption.

"With the introduction of the modular CRM system, new opportunities are provided to further individualize patient treatment," they write.